1. Field of the Invention
The present invention relates to a method of initializing a magnetooptical recording medium having tracks onto which information is recorded formed in parallel and having intermediate regions between the tracks, and to an apparatus for executing this method.
2. Related Background Art
Hitherto, a typical medium, which is used in a magnetooptical storing apparatus, has a construction as shown in FIG. 1.
In FIG. 1, reference numeral 22 denotes a substrate. A magnetic film 23 is formed on the surface of the substrate 22. As shown in the diagram, convex-shaped tracks (hereinafter, referred to as "lands") 21 on which information is recorded are formed on the medium. Two non-recording intermediate regions (hereinafter, referred to as "grooves") 20 are formed as concave portions (grooves) at positions adjacent to a land 21. Information is recorded by irradiating a spot-shaped laser beam LB onto a land while applying a bias magnetic field thereto.
Since the magnetizing directions of the magnetic film 23 formed upon manufacturing of the medium are random, the magnetizing directions of the magnetic layer must be once aligned into a predetermined direction and must be initialized. On the other hand, in the case of rewriting over the information recorded on the medium, it is also necessary to initialize prior to rerecording.
The initializing operation is executed in a manner such that the laser beam LB having an erasing power is irradiated onto a land 21 while applying a bias magnetic field in a direction opposite to the bias magnetic field applied upon recording, and a laser beam spot is formed and the land 21 is scanned by the beam spot. Upon scanning, automatic focusing (AF) and automatic tracking (AT) are executed so as to allow the beam spot of a proper size to be located onto the land and to always obtain a state as shown by a spot SP.sub.1.
Therefore, ideally, only the magnetizing directions of the land 21 are aligned in the predetermined direction by the erasing operation.
However, actually, even if the AF and AT are executed, a case occurs wherein the laser beam is partially deviated like a spot SP.sub.2 with respect to the groove 20. On the other hand, in the case of using a push-pull system a means for performing the AT, the laser beam to record, reproduce, and erase information is also used as a beam for the AT, so that the beam spot has a configuration so as to be always partially deviated like a spot SP.sub.3 with respect to the groove 20.
In the cases of the spots SP.sub.2 and SP.sub.3 as mentioned above, the laser beam is also irradiated onto a portion of the groove 20. However, the power of the beam which is irradiated onto the groove is so small that the initializing operation to align the magnetizing directions in a predetermined direction is not substantially executed for the groove, and the random magnetizations remain.
Upon recording of information, the laser beam LB having the recording power is irradiated onto the land 21 while applying the bias magnetic field in the direction applied opposite to the direction upon initialization, a beam spot is formed, the land 21 is scanned by the beam spot, and the laser beam is turned ON and OFF in accordance with the information to be recorded. Even in the case of the recording mode, the states of the spots SP.sub.2 and SP.sub.3 shown in the diagram are realized, since the power of the laser beam which is irradiated onto the groove 20 is also small, similar to the case in the erasing mode, so that the recording operation is not substantially executed for the groove, and the random magnetizations remain.
The information recorded on the medium is reproduced by detecting the reflected lights from the spot. However, it is virtually impossible to form the beam spot so as not to deviate from the land 21. Therefore, the reflected lights from the medium include those lights reflected from a portion of the land 21 and those lights reflected by a portion of the groove 20.
As mentioned above, since the magnetizing directions of the groove 20 are maintained random, the signal components due to the reflected lights from the portion of the groove 20 generate noise for the normal signal due to the reflected lights from the portion of the land 21.
Consequently, the conventional magnetooptical storing apparatus has a problem such that a reproducing error rate is somewhat high.